Tuesday, June 12, 2018

Curiosity Rover has discovered methane and other organic compounds on Mars. But these need not be linked to incipient life forms.

As is often the case, the yen among astronomers to find life - of any kind - often leads to 'jumping the gun' before all the data has been vetted. Such is the case again after Curiosity Rover was claimed to have found "potential signs of life on Mars." This was based on the detection of methane— as well as apparent traces of organic compounds in ancient mudstone.Curiosity landed on Mars back in 2012 and it’s been slowly climbing up Mount Sharp, a large hill formed when an asteroid impact created Gale Crater, simultaneously exposing multi-billion year old sedimentary rocks laid down in an ancient lakebed. The rover came equipped with a suite of instruments known as Sample Analysis at Mars, or SAM. And its main goal was to find organic molecules. These commonly form in non-biological processes, but they’re also the building blocks of life.
And mysteriously, the VW Beetle-sized rover succeeded in finding organics even though past Mars missions, like 1976’s Viking landers, did not. (But bear in mind the detection technology available to the Viking craft was vastly inferior to what Rover has to work with.) Anyway, Rover's data has led to two scientific papers published simultaneously in the prestigious journal Science. In the first paper, a team analyzed three Mars years worth (55 Earth months) of atmospheric data from Curiosity. In that time, the rover caught methane levels spiking as the seasons changed, growing several times stronger at the height of summer in the northern hemisphere. Note that on Mars methane levels range between 0.24 to 0.65 parts per million. This is compared to a level of about 1800 parts per billion on Earth.
Based on the chemical make-up, the scientists suspect this methane was heated up and released from sub-surface reservoirs where it was likely trapped in permafrost. They suspect large amount of the gas may be frozen in such underground reservoirs. But its exact origin remains a mystery.

The second paper was based on a study, led by NASA bio-geochemist Jennifer Eigenbrode, examined drill samples of three-billion year old mudstones that Curiosity collected from two different sites in Gale Crater. Curiosity Rover dropped these samples into an onboard laboratory and cooked them in order to analyze the gasses they threw out.According to Eigenbrode’s team, the rocks released organic molecules much like those found in organic-rich rocks on Earth. The core problem? There is simply no way to determine if these molecules are evidence of ancient Martian life.
This is far from the first time Mars researchers have claimed to find methane. Curiosity itself made headlines in recent years after seeing faint methane signals. But scientists have been chasing this gas for decades. This alone ought to put a damper on too much excitement that the source of the CH4 is some kind of life form.What is the most likely cause of the new methane signals? Not life, but rather a leakage from water-based crystals called clathrates, these buried in the cold Martian soil. Seasonal changes in temperature would then release different amounts of methane, more as the temperature increases..The most resonant question then remains: Are there now signs of life on Mars?In the words of Michael Meyer, lead scientist for NASA's Mars Exploration Program:"We don't know but these results tell us we are on the right track."As indeed we presumably have been for the past 4 decades.

About Me

Specialized in space physics and solar physics, developed first astronomy curriculum for Caribbean secondary schools, has written thirteen books - the most recent:Fundamentals of Solar Physics. Also: Modern Physics: Notes, Problems and Solutions;:'Beyond Atheism, Beyond God', Astronomy & Astrophysics: Notes, Problems and Solutions', 'Physics Notes for Advanced Level&#39, Mathematical Excursions in Brane Space, Selected Analyses in Solar Flare Plasma Dynamics; and 'A History of Caribbean Secondary School Astronomy'. It details the background to my development and implementation of the first ever astronomy curriculum for secondary schools in the Caribbean.